How does an end-blown flute differ from a side-blown flute?

The primary difference between end-blown and side-blown flutes lies in how the player directs their breath to produce sound, a process known as edge-tone generation.1

• End-blown flutes: The player directs their breath across the sharp rim at the upper, open end of the tube. In many traditions, a notch may be cut into the edge of the tube to facilitate this sound production. Examples include the Arabic nāy, the Japanese shakuhachi, and panpipes.123
• Side-blown (transverse) flutes: The player blows across a lateral embouchure hole located on the side of the instrument, directing the airstream against the far edge of that opening. This is the design characteristic of the modern orchestral flute and piccolo.312

Both types are classified as "true flutes" because the player shapes the airstream with their lips, distinguishing them from fipple flutes (such as the recorder), which use an internal duct to guide air against the edge.312